This invention relates to a electrostatographic reproduction machine architecture, and more particularly, such a machine having a photoreceptor belt conicity reducing support assembly.
A typical electrophotographic or electrostatographic reproduction machine employs a photoconductive member that is charged to a substantially uniform potential so as to sensitize the surface thereof. The charged portion of the photoconductive member is exposed to a light image of an original document being reproduced. Exposure of the charged photoconductive member selectively dissipates the charge thereon in the irradiated areas to record an electrostatic latent image on the photoconductive member corresponding to the informational areas contained within the original document.
After the electrostatic latent image is recorded on the photoconductive member, the latent image is developed by bringing a developer material into contact therewith. Generally, the electrostatic latent image is developed with dry developer material comprising carrier granules having toner particles adhering triboelectrically thereto. However, a liquid developer material may be used as well. The toner particles are attracted to the latent image, forming a visible powder image on the photoconductive surface. After the electrostatic latent image is developed with the toner particles, the toner powder image is transferred to a sheet. Thereafter, the toner image is heated to permanently fuse it to the sheet.
It is highly desirable to use an electrostatographic reproduction machine of this type to produce color prints. In order to produce a color print, the electrostatographic reproduction machine includes a plurality of stations. Each station has a charging device for charging the photoconductive surface, an exposing device for selectively illuminating the charged portions of the photoconductive surface to record an electrostatic latent image thereon, and a developer unit for developing the electrostatic latent image with toner particles. Each developer unit deposits different color toner particles on the respective electrostatic latent image. The images are developed, at least partially in superimposed registration with one another, to form a multi-color toner powder image.
The resultant multi-color powder image is subsequently transferred to a sheet. The transferred multi-color image is then permanently fused to the sheet forming the color print. Hereinbefore, a color electrostatographic reproduction machine used four developer units. These developer units were all disposed on one side of the photoconductive belt with the other side thereof being devoid of developer units. A color electrostatographic reproduction machine of this type required an overly long photoconductive belt. A photoconductive belt of this type would require eleven, nine-inch pitches to operate at 100 ppm. A belt of this length will have very low yields when being made in large quantities. In addition, this results in an overly tall electrostatographic reproduction machine when the photoconductive belt is arranged with the major axis aligned vertically. The requirement of having all of the developer units or exposure stations on one side of the photoconductive belt is necessary in order to maintain image-on-image registration. Thus, it is highly desirable to reduce the overall height of the electrostatographic reproduction machine while still maintaining the required image-on-image registration.
Various different architectures for multi-color electrostatographic reproduction machines have heretofore been employed. For example, U.S. Pat. No. 4,998,145 discloses an electrophotographic electrostatographic reproduction machine having a plurality of developer units adjacent one another on one side of the diameter of a photoconductive drum.
U.S. Pat. No. 5,270,769 describes a electrostatographic reproduction machine having a plurality of developer units disposed on one side of a photoconductive belt. A cleaning unit is positioned on the other side of the photoconductive belt. Different colored developed images are transferred to an intermediate belt. The resultant composite multi-color image is then transferred from the intermediate belt to a sheet of support material and fused thereto. The photoconductive belt is arranged vertically.
U.S. Pat. No. 5,313,259 discloses a multi-color electrophotographic electrostatographic reproduction machine in which an endless photoconductive belt is vertically oriented. The machine includes four groups of stations for printing in cyan, magenta, yellow, and black. Each station includes a charged corona generator, a raster output scanning laser assembly, and a developer unit. These stations are positioned on one side of the photoconductive belt with the fourth station being disposed on the other side thereof. Successive different color toner particle images are formed in superimposed registration with one another on the photoconductive belt and transferred to a copy sheet simultaneously. Transfer occurs at the lowermost position of the photoconductive belt.
Typically, in these conventional machine architectures, the endless photoconductive belt is arranged into two sides or spans (a slack span and a tension span) that are supported vertically, about a drive roll, skid backer bars, a stripper roll, and a steering and tensioning roll. As such the belt has, and is moved in, a generally elliptical configuration that includes a single free major axis.
Unfortunately, when there are many skid backer bars on both the slack side and the tension side of the configuration, the single free major axis of belt movement becomes less responsive to belt conicity. As an undesirable consequence, belt conicity compensation of the architecture is compromised. In addition, when the drive roll pushes the belt towards its slack span, drag on the many skid backer bars produces a stiff tension drive between spans, resulting in belt undesirable shear and belt wrinkle.
In accordance with one aspect of the present invention, there is provided an electrostatographic reproduction machine including a media assembly for supplying and moving toner image receiving media passed a toner image transfer device; a fusing apparatus for heating and fusing a toner image on the toner image receiving media; and an imaging assembly for forming and transferring a toner image onto the toner image receiving media. The imaging assembly includes an endless photoreceptor belt having an imageable surface for forming the toner image, and a conicity reducing belt support and moving subassembly for supporting and moving the endless photoreceptor belt. The conicity reducing belt support and moving subassembly includes (i) a moveable steering roll for moving in a first direction into the endless photoreceptor belt and in a second direction along an inner surface of the endless photoreceptor belt, and (ii) a moveable tensioning roll for moving in a third direction into the endless photoreceptor belt and in a fourth direction along the inner surface of the endless photoreceptor belt, thereby reducing belt conicity and belt wrinkle, and increasing belt lateral registration.